Heretofore, plant tissue culture vessels or containers have been known and capable of providing various growth conditions as in the vessel disclosed in U.S. Pat. No. 4,358,908. However, this vessel may not be operated to easily adjust the gas exchange rate between the interior and the ambient, and it is not economical to use non-autoclavable filters for such a vessel. Some plant tissue culture containers do not have filters and filters used in others are not fine enough to filter out dust, bacteria or virus. It has been known to minimize contamination by growing plant tissue cultures in clean chambers that have filtered air. Such clean chambers are expensive to construct, operate and maintain. Even so, because of personnel and material traffic through clean chambers, some contamination through gas exchange cannot be avoided. Since known plant tissue culture containers or vessels are not in themselves contamination-proof, the plant tissue cultures are not free from contamination even in clean room environments.
Because known culture containers are not contamination-free, they must be sealed with tape during shipping. The tape seals are often damaged and the media within the container is disturbed when the containers are suddenly subjected to lower air pressure as during air shipping. Such containers do not allow equalizing air pressure with contamination-free air exchange. Those containers with tight tape seals do not allow sufficient gas exchange, thereby preventing proper plant growth.
Currently used containers have generally fixed spacing between cover and base for gas exchange. Such fixed spacing is excessive for some cultures particularly when the cultures are grown over long periods of time and insufficient for others. Other containers are too tight and therefore do not allow sufficient gas exchange, thereby retaining ethylene or moisture to prevent proper plant growth. Present containers cannot readily adjust the gas exchange rate.
Covers of known containers or vessels are tightly mounted on or screwed onto the base, thereby requiring both hands of a laboratory technician to close or remove the cover. The cover for the container of the above patent fits tightly on the base. This leads to inefficiency in container handling and higher costs, particularly during transplanting at the hood. Some current covers have totally loose covers which are not safe when the units are moved around during handling, and it is preferable to have tightly held covers during shipping and even during incubation. No known culture container allows for the adjustment of the tightness of the cover on the base.
When culturing different plants, containers of different heights are needed. For operations at the hood, planting or transplanting, when the body or base of the container is lower, it is easier to reach and more efficient. For most plants, the bases have to be tall enough to prevent the leaves from falling over the edges to allow the covers to be reclosed. Containers with short bases and tall covers are preferred for plants that grow straight up. Current reusable containers cannot be used upside-down in order to change the relative heights of the covers and bases because they include a drip ring, usable only in the upright position, to prevent condensation forming after autoclaving from leaking into the opening between the cover and base and causing contamination.
Heretofore, most plastic covers for plant tissue culture vessels are made of polypropylene for flexibility and autoclavability features. Polypropylene is objectionable in that it is translucent and does not allow total light transmission, thereby losing some light energy.
Satisfactory filters heretofore used have been expensive and difficult to manufacture. Further, known filters or filtering tapes are not fine enough to filter dust, bacteria or virus. Some permeable tapes do not allow enough gas exchange.